1. Field of the Invention
This invention relates, in general, to high-temperature materials and, in particular, to a new class of oligomeric arylether-containing phthalonitriles containing of varying average molecular weight, their conversion to high-temperature thermosetting polymers, and the synthesis thereof.
2. Description of the Background Art
Phthalonitrile polymers constitute a recent and important class of high-temperature materials, having a wide range of uses, such as composite matrices, adhesives, sealants, and even semiconductors. These polymers have been developed to address the shortcomings of current commercially available thermosetting resins. For example, U.S. Pat. No. 4,409,382, (the entirety of which is incorporated by reference) to Keller, discloses a family of phthalonitrile polymers related to that of the present invention.
Phthalonitrile polymers are prepared from phthalonitriles in which the linking group between the two ortho dinitrile groups separates the dinitrile groups enough to permit polymerization. This polymerization takes place through the nitrile groups by an addition mechanism yielding heterocyclic crosslinked products known to exhibit good thermal and oxidative properties. The phthalonitrile resins can be reacted to a prepolymer stage and stored indefinitely at room temperature without further reaction. The polymerization occurs above the melting point or glass transition temperature and is controlled as a function of the amount of curing additive and the curing temperature.
Several aromatic phthalonitrile resins with ether, thioether, sulfone, and imide linkages have been previously reported and patented. When the melt of the monomers are heated in the absence or presence of metallic or organic nucleophilic co-reactants, e.g., aromatic amines, polymerization occurs to afford thermosetting polymeric materials which exhibit superior thermo-oxidative properties relative to currently used commercial high temperature polymers. When fully cured, these polymers exhibit glass transition temperatures in excess of 400.degree. C.